Like @maxonss said, welcome to the community. And thanks for trying out SuiteCRM 8 RC.
At the moment SuiteCRM 8 install process expects the database password to be filled, its a required field. As of now, there is no way to override this.
I’m going to raise this internally to understand if this having a blank db password is something we would like to support.
The SuiteCRM install process, before executing the actual install, does some checks.
One of those checks is to see if SuiteCRM is able to access the db using the credentials provided.
The error you are seeing is exactly that. SuiteCRM is not able to connect to the database on localhost using user root and the password you provided.
Could you try 127.0.0.1, instead of localhost, please? with localhost it symfony / doctrine tries to use the socket connection by default, and will fail if not setup.